A senior official of the Nigerian government on Thursday told BBC that 21 of the 275 Chibok girls kidnapped by militants of the Boko Haram group have been released. According to the report, they are being held by security services in Maiduguri city around 130 km from Chibok town. It is unclear how the girls were rescued.

However, two spokespersons for President Muhammadu Buhari told Reuters that they were not aware of any of the Chibok girls being released. The Nigerian Army is in the process of conducting a "large-scale operation" in Boko Haram stronghold, the Sambisa forest, where the first Chibok girl was rescued in May.

Website Africa News cited local reports and said that the girls were picked up by a military helicopter after the militant group dropped them in Borno state. Activist group Bring Back Our Girls, which was formed after at least 275 girls were taken from a school in Chibok on the night of April 14, 2014, said they were monitoring the news. "This will be extremely happy news if true," the group said on Twitter.

In August, Boko Haram had released a video in which around 50 of the girls could be seen with a gunman. In the clip, the militant group had demanded the release of its fighters in exchange for the girls' release. The gunman had also claimed that some girls had died in airstrikes launched by the Army.

The girls' kidnapping had triggered a social media campaign, #BringBackOurGirls, which several well-known personalities took part in, including First Lady Michelle Obama.